1. Field of the Invention
The present invention relates to a vehicle collision sensing system, which senses a collision to a lateral surface of a vehicle.
2. Description of Related Art
For example, Japanese Unexamined Patent Publication No. H02-249740 recites a pressure sensor, which is arranged in an interior of a vehicle door and serves as a side collision sensing means for sensing a collision to a lateral surface of a vehicle (a side collision of the vehicle) and for activating an occupant protective device (e.g., a side air bag) upon occurrence of the side collision. According to Japanese Unexamined Patent Publication No. H02-249740, an air tightly sealed air tank is placed in the interior of the vehicle door, and a pressure inside the air tank is sensed with the pressure sensor. When the pressure of the air tank, which is sensed with the pressure sensor, becomes equal to or greater than a predetermined threshold value, it is determined that an object collides with a side of the vehicle, and thereby the air bag or the like is activated.
In the case of Japanese Unexamined Patent Publication No. H02-249740, an accommodating space for accommodating the air tank is required in the interior of the vehicle door. Thus, there are limitations in terms of the designing of the vehicle door and the air tank. Furthermore, the provision of the air tank causes an increase in the costs. In order to address the above disadvantages, it is conceivable to sense the side collision of the vehicle by directly sensing the pressure in the vehicle door interior space with a pressure sensor. Specifically, the pressure of the vehicle door interior space is compared with a predetermined threshold value to sense occurrence of the collision of the vehicle.
However, the pressure of the vehicle door interior space may significantly change when the atmospheric pressure changes due to a change in an altitude of the current location of vehicle or a change in weather of the current location of the vehicle. Thus, in the case where such a pressure of the vehicle door interior space is compared with the predetermined threshold value to sense the occurrence of the collision of the vehicle, the occurrence of the collision of the vehicle may not be accurately sensed. This is also true in the above case where the air tank is used to sense the occurrence of the collision of the vehicle.
In view of this, it is also conceivable to use a pressure change amount, i.e., an amount of change in the pressure of the vehicle door interior space to sense the occurrence of the collision instead of the pressure in the vehicle door interior space. However, the pressure change amount varies when the atmospheric pressure changes even in the case where the amount of change in the interior space of the vehicle door is the same. That is, the occurrence of the collision may not be accurately sensed even when the pressure change amount is used.